1. Field of the Invention
The present invention is directed to a bioreactor for the ex vivo growth of normal mammalian cells, especially the maintenance and selective growth of human stem and/or hematopoietic cells.
2. Background of the Invention
There is a significant interest in the ability to use cells for a wide variety of therapeutic purposes. The hematopoietic system exemplifies an extraordinary range of cells involved in protection of mammalian hosts from pathogens, toxins, neoplastic cells and other diseases. The hematopoietic system is believed to evolve from a single stem cell, from which all the lineages of the hematopoietic derive. The hematopoietic cells are known to grow and mature to varying degrees in bone as part of the bone marrow. It therefore becomes of interest to recreate a system which provides substantially the same environment as is encountered in the bone marrow, as well as being able to direct the cells which are grown in culture to a specific lineage. This is described in greater detail in U.S. patent application Ser. No. 08/178,433 filed on Jan. 6, 1994, now U.S. Pat. No. 5,459,069, which is a continuation of U.S. patent application Ser. No. 07/845,969, filed on Mar. 4, 1992 and now abandoned, and which is a continuation in part of U.S. patent application Ser. No. 07/366,639, filed on Jun. 15, 1989, and now also abandoned. The above applications are herein incorporated by reference into the present application. Also here incorporated by reference is our new U.S. patent application entitled "APPARATUS AND METHOD FOR MAINTAINING AND GROWING BIOLOGICAL CELLS," filed on Jun. 7, 1995 by the firm of Schroeder, Brueggemann & Clark of Los Angeles, Calif., and having attorney docket no. P03 33674 U.S. patent application Ser. No. 08/483,520, now abandoned.
The particular manner in which human stem cells proliferate and differentiate into their lineage is not completely understood, nor are the factors defined. However, once a human stem cell has become dedicated to a particular lineage, there appear to be a number of factors, for example colony stimulating factors, which allow, and may direct, the stem cell to a particular mature cell lineage. These colony stimulating factors include the oxygen concentration, and the rate of flow of, and the concentration of nutrients and waste products in, a liquid growth medium within which the cell colony is perfused.